An inkjet printing system typically includes one or more printheads and their corresponding ink supplies. Each printhead includes an ink inlet that is connected to its ink supply and an array of drop ejectors, each ejector consisting of an ink pressurization chamber, an ejecting actuator and a nozzle through which droplets of ink are ejected. The ejecting actuator may be one of various types, including a heater that vaporizes some of the ink in the pressurization chamber in order to propel a droplet out of the nozzle, or a piezoelectric device which changes the wall geometry of the chamber in order to generate a pressure wave that ejects a droplet. The droplets are typically directed toward paper or other recording medium in order to produce an image according to image data that is converted into electronic firing pulses for the drop ejectors as the recording medium is moved relative to the printhead.
Drop ejector arrays (sometimes interchangeably called nozzle arrays herein) are typically fabricated on printhead die at the wafer scale using integrated circuit and MEMS (micro-electrical-mechanical systems) fabrication techniques. Printhead die for some types of inkjet printing technologies, such as thermal inkjet, can include integrated logic and driver circuitry as well as drop ejector arrays, bond pads for electrical interconnection, and an ink feed opening for each separate drop ejector array. The microelectronic and microfluidic packaging of a printhead die into a printhead assembly includes electrical interconnection to facilitate providing signals and power to the small bond pads on the printhead die; mechanical and environmental protection for the printhead die and the electrical interconnections; provision of alignment features to facilitate alignment of the small drop ejectors in the printer for good image quality; and fluidic connection to facilitate providing ink from relatively large ink supplies to relatively small ink feed openings on the printhead die. In other words, much of the printhead assembly facilitates interfacing with small and fragile features of the printhead die, so that the printhead can be readily and reliably installed and used in the printer, even by an untrained user.
A typical early step of printhead assembly is the adhesive bonding of the one or more printhead die to a mounting member using a precisely dispensed adhesive that provides ink resistant fluidic seal(s) between one or more ink feed openings on the one or more printhead die to corresponding opening(s) on the mounting member. Commonly assigned U.S. Patent Application Publication No. 2008/0149024, incorporated herein by reference, discloses a mounting member (made of ceramic, for example) that is insert molded into a substrate. The mounting member includes fluid channels, each of which provides fluid to a corresponding array of drop ejectors. Commonly assigned U.S. Patent Application Publication No. 2008/0202694, incorporated herein by reference, discloses a bismaleimide-containing adhesive sealant for bonding an inkjet printhead die to a mounting member.
Inkjet ink includes a variety of volatile and nonvolatile components including pigments or dyes, humectants, image durability enhancers, and carriers or solvents. A key consideration in ink formulation and ink delivery is the ability to produce high quality images on the print medium. Image quality can be degraded if evaporation of volatile components in the vicinity of the nozzle causes the viscosity to increase too much. The maintenance station of the printer typically includes a cap that surrounds the printhead die nozzle face during periods of nonprinting in order to inhibit evaporation of the volatile components of the ink, and also to provide protection against accumulation of particulates on the nozzle face. The maintenance station also typically includes a wiper for wiping the nozzle face to clean off ink residue and other debris.
A common type of printer architecture is the carriage printer, where the printhead nozzle array is somewhat smaller than the extent of the region of interest for printing on the recording medium and the printhead is mounted on a carriage. In a carriage printer, the recording medium is advanced a given distance along a media advance direction and then stopped. While the recording medium is stopped, the printhead is moved by the carriage in a carriage scan direction that is substantially perpendicular to the media advance direction as the drops are ejected from the nozzles. After the printhead has printed a swath of the image while traversing the recording medium, the recording medium is advanced, the carriage direction of motion is reversed, and the image is formed swath by swath.
In an inkjet printer, the face of the printhead die containing the nozzle array(s) is typically positioned near the recording medium in order to provide improved print quality. Close positioning of the nozzle face of the printhead die to the recording medium keeps the printed dots close to their intended locations, even for angularly misdirected jets. Typically the nozzle face is recessed slightly below other features, such as encapsulation. Electrical interconnection to the bond pads on the printhead die is provided by wire bonding or tape automated bonding to a flexible printed wiring member. The electrical interconnections must be protected mechanically and environmentally for long-term reliability of the printhead. Flow of the encapsulant for the electrical interconnections must be carefully controlled before curing in order to provide a low profile printhead face that allows close positioning and good maintainability of the nozzle face. An encapsulation process for printhead die electrical interconnections is disclosed in commonly assigned U.S. Patent Application No. 2008/0158298, incorporated herein by reference.
Although the typical printhead assembly configuration and method is suitable in many applications, there is a need to provide improved control of encapsulant near the nozzle face, to use fewer different materials, and to eliminate relatively expensive components and processes, such as the ceramic mounting member for the printhead die, as well as precision dispensing of adhesive.